1. Field of the Invention
The present invention relates to a method of manufacturing a liquid ejection head for ejecting liquid such as ink.
2. Description of the Related Art
Various techniques are being employed in the field of electronic packaging for the purpose of applying liquid such as an adhesive agent or an encapsulant material to the surface of a substrate to which an IC (integral circuit) chip or a wiring substrate is to be bonded. Known such techniques include, for example, a technique of applying liquid in a lump to a substrate with use of a transfer plate and a technique of ejecting liquid through a thin needle fitted to a syringe that is filled with liquid for painting application.
Meanwhile, there is another known technique of applying liquid to a substrate by squeegeeing liquid onto a rotating roller to a desired thickness in advance and transferring the liquid onto the substrate while driving the roller to touch and traverse the substrate. Such liquid transfer using a roller is being widely employed in the field of printing. For example, ink is laid on an offset roller to a desired thickness and a sheet of paper is pressed against the roller for ink transfer in an offset printing operation. Such a technique of transferring liquid by means of a roller can be used to apply liquid onto a substrate to a desired thickness so as to achieve an excellently uniform distribution of thickness if the thickness of the liquid on the roller is controlled. Additionally, the technique of transferring liquid by means of a roller can reduce the time required to apply liquid and hence can apply liquid in a lump for a uniform distribution of thickness in a short period of time. Thus, this technique of transferring liquid by means of a roller has a wide range of potential applications of applying liquid such as an adhesive agent or an encapsulant material to the surface of a substrate in the field of electronic packaging.
In the field of electronic packaging, for instance, Japanese Patent Application Laid-Open No. 2002-131764 discloses a method of applying an encapsulant material to a substrate and Japanese Patent Application Laid-Open No. 2005-116917 discloses a method of using a roller to apply molten solder to a substrate as transfer and application techniques using a roller.
As described above, liquid can be applied uniformly and relatively easily onto the entire surface of a substrate by using such a technique of transferring and applying liquid onto a substrate by means of a roller. For example, an adhesive agent can efficiently be applied to a substrate by using such a technique of transferring and applying an adhesive agent onto a substrate by means of a roller.
However, there are instances where a substrate does not have a uniform and plane surface in the field of electronic packaging. For example, plate substrates to be used for liquid ejection heads are provided with a liquid supply port as an aperture for supplying ink to a recording element substrate arranged on the substrate surface. This liquid supply port is a through hole extending from the front surface to the rear surface of the plate substrate and takes an important role for supplying ink to a recording element substrate. Then, as an adhesive agent, for example, for bonding a recording element substrate to the plate substrate is transferred and applied to the latter by means of a roller, the adhesive agent can get into the liquid supply port depending on the physical properties of the adhesive agent.
As the adhesive agent gets into the liquid supply port, the adhesive agent closes part of the liquid supply port, which can change the flow rate of ink flowing through the liquid supply port. Particularly in the case of a liquid ejection head that has a plurality of liquid supply ports, the size of the aperture of each of the liquid supply ports can be changed by the adhesive agent that has gotten into the liquid supply port, to by turn change the ink flow rate of each of the recording element substrates to consequently give rise to a problem to the printing performance of the liquid ejection head.
Furthermore, when a liquid ejection head has small liquid supply ports, the adhesive agent that has gotten into the liquid supply ports can completely clog them.